title: Characterization of N-acylhomoserine lactone-degrading bacteria associated with the Zingiber officinale (ginger) rhizosphere: co-existence of quorum quenching and quorum sensing in Acinetobacter and Burkholderia.
abstract: BACKGROUND
  Cell-to-cell communication (quorum sensing (QS)) co-ordinates bacterial behaviour at a population level. Consequently the behaviour of a natural multi-species community is likely to depend at least in part on co-existing QS and quorum quenching (QQ) activities. Here we sought to discover novel N-acylhomoserine lactone (AHL)-dependent QS and QQ strains by investigating a bacterial community associated with the rhizosphere of ginger (Zingiber officinale) growing in the Malaysian rainforest.
  
  
  RESULTS
  By using a basal growth medium containing N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) as the sole source of carbon and nitrogen, the ginger rhizosphere associated bacteria were enriched for strains with AHL-degrading capabilities. Three isolates belonging to the genera Acinetobacter (GG2), Burkholderia (GG4) and Klebsiella (Se14) were identified and selected for further study. Strains GG2 and Se14 exhibited the broadest spectrum of AHL-degrading activities via lactonolysis while GG4 reduced 3-oxo-AHLs to the corresponding 3-hydroxy compounds. In GG2 and GG4, QQ was found to co-exist with AHL-dependent QS and GG2 was shown to inactivate both self-generated and exogenously supplied AHLs. GG2, GG4 and Se14 were each able to attenuate virulence factor production in both human and plant pathogens.
  
  
  CONCLUSIONS
  Collectively our data show that ginger rhizosphere bacteria which make and degrade a wide range of AHLs are likely to play a collective role in determining the QS-dependent phenotype of a polymicrobial community.
authors.affiliation: Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia. kokgan@um.edu.my
authors.forename: Kok-Gan
authors.initials: KG
authors.lastname: Chan
authors.forename: Steve
authors.initials: S
authors.lastname: Atkinson
authors.forename: Kalai
authors.initials: K
authors.lastname: Mathee
authors.forename: Choon-Kook
authors.initials: CK
authors.lastname: Sam
authors.forename: Siri Ram
authors.initials: SR
authors.lastname: Chhabra
authors.forename: Miguel
authors.initials: M
authors.lastname: Cámara
authors.forename: Chong-Lek
authors.initials: CL
authors.lastname: Koh
authors.forename: Paul
authors.initials: P
authors.lastname: Williams
mesh_terms: D000150:Acinetobacter / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D054742:Acyl-Butyrolactones / Q000378:metabolism*; D019117:Burkholderia / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D003470:Culture Media; D020939:Zingiber officinale / Q000382:microbiology*; D008296:Malaysia; D053038:Quorum Sensing; D058441:Rhizosphere
chemical_list: D054742:Acyl-Butyrolactones; D003470:Culture Media